The effect of non-heterosexual factors on the vaginal flora has been studied. Ninety-one lesbians attending a specialist genitourinary medicine service for lesbians were studied. Bacterial vaginosis (BV) was diagnosed in 51.6% of them. While most of the women had previously had a male sexual partner, the presence of BV was not associated with a male sexual partner in the previous 12 months. A detailed analysis of lesbian sexual practices in the group did not relate BV to any sexual practice which would have the propensity to pass vaginal secretions from one to the other.